w = int(input())
h = int(input())
n = int(input())

wd = set()
hd = set()

wc = 0
hc = 0

for i in range(n):
  a, b = [int(x) for x in input().split()]
  
  if a not in wd:
    wd.add(a)
    wc += 1
  
  if b not in hd:
    hd.add(b)
    hc += 1
    
print(w * h - ((w - wc) * (h - hc) + n))